Re: [gentoo-user] is multi-core really worth it?

[Peter Humphrey <peter@prh.myzen.co.uk>]

On Tuesday, 5 December 2017 04:11:17 GMT Taiidan@gmx.com wrote:
> On my 16 core opteron I have to do -j32 or sometimes -j64 to be using
> everything all the time, is this normal? If I don't do this it won't be
> pegged at 100% all the time.

On my 12-thread i7 I have -j24 -l60. Most times it's better not to limit the
number of jobs, just the load average; then portage loads up the CPU as high
as it can.

The exception, and even this is debatable, is when you're compiling a large
set of packages, say an emerge -e world, in which case so many jobs have
been started by the time they're all into compiling that the load soars to
silly heights - I've seen 80-odd here. But that's only about seven jobs
queued per CPU thread, so maybe it isn't too bad after all.

> I assume using a ramdisk would help with this? I wouldn't want to do a
> SSD as I assume it would excessively wear by doing compiles.

I use tmpfs, like this:

$ grep tmpfs /etc/fstab
tmpfs   /var/tmp/portage  tmpfs   noatime,uid=portage,gid=portage,mode=0775  0 0
tmpfs   /tmp                      tmpfs   noatime,nosuid,nodev,noexec,mode=1777   0 0

If a tmpfs fills up, the excess gets swapped out, but with 32GB RAM here I
haven't yet seen any swap used at all - not even in an emerge -e world.

I've read that modern SSDs are far less prone to wear than earlier ones, as
R0b0t1 suggests.

-- 
Regards,
Peter.